Quantitative label-free screening for antibodies using scattering biophotonic microarray imaging

A biophotonic array based on gold nanoparticles functionalized with antigen proteins has been used to determine the concentrations of the respective antibodies in solution. Four proteins—fibrinogen, bovine serum albumin, transferrin, and C-reactive protein—were used to construct a test array with the assay repeated a number of times. The antibody–antigen association and dissociation rate constants were determined for the antibody assays from a series of calibration experiments. The label-free determination of the unknown antibody concentrations was performed using two related kinetic analyses. From these results, the current array assay sensitivity is 250 ng ml–1 with an accuracy of 15% using an 8-min kinetic measurement and a 16-spot averaged assay.